Controller for direct-current motors



Aug. 26, 1924- w. H. LESLIE CONTRQLLER FOR DIRECT CURRENT MOTORS Filed Oct. 13. 1923 INVENTEIR UIHML .owaxwUW Patented Aug. 26, 1924.

PATENT OFFICE.

WILLIAM H. LESLIE, F TOR-ONTO, QN'IABIO, CANADA.

CONTROLLER FOB DIRECT-CURRENT MOTOR-S.

Application filed October 13, 1923.

T 0 all whom it may concern:

Be it known that I, WVILLIAM H. LnsLrn. of the city of Toronto, in the county of York, Province of Ontario, Canada, a subject of the King of Great Britain, have invented certain new and useful Improvements in Controllers for Direct-Current Motors, of which the following is a specitication.

This invention relates to controllers for changing the speed of direct current electric motors. It is usual in such controllers to provide asolenoid controlled plunger which reciprocates between two extreme positions one of which it occupies when the motor is at maximum speed and the other when it is at minimum speed, the speed control being obtained by varying the resistance in the field and armature circuits of the motor.

My object in the present invention is to provide means whereby the minimum speed may be varied without adding to the electrical equipment or varying the stroke of the plunger.

I attain my objects by means of the constructions hereinafter described and illustrated in the accompanying drawings in which Fig. 1 is a front elevation of part of a motor control constructed in accordance with my invention;

Fig. 2 a sectional detail of part of the same; and

Fig. 3 a side elevation, partly in section, of a modification.

1 is a solenoid, the winding of which is in a circuit adapted to be opened and closed by means of a switch (not shown). 2 is a plunger, the upper part of which forms the core of the solenoid. On this plunger a crosshead 3 is slidable. This crosshead car ries a plurality of contacts; which are adapted to contact with one or more series of stationary contacts which control resistances in the armature and field circuits of the motor to be controlled.

The contacts 4 on the plunger are all spring pressed and are of known construe tion. At opposite sides of the plunger on suitable supports 5 are carried the fixed contacts 6. As is known in the art, these contacts will be arranged so that the motor is running at full speed with the crosshead in its uppermost position and at minimum Serial No. 868,437.

when the plunger is in its lowermost position. It is evident therefore that if the lowermost position of the crosshead be varied. the minimum resistance of the motor circuits may be varied and thus the minimum speed of the motor adjusted as may be desired.

Fo the purpose of adjusting the crosshead, I form a rack 7 on the lower part of the plunger 2. In the extension 8 of the crosshead I journal a spindle 9, on which is formed or secured a pinion 1O meshing with the rack. In the preferred arrangement, keyhole slots 11 are formed in the sides of the extension 8, the smaller ends of these slots forming bearings for the spindle, while the larger portions permit of the spindle and pinion being introduced from one side or the other of the extension, these enlarged portions of the slots being sufiicient for the passage of the pinion.

A spring actuated click 12 operates through an opening in the side of the extension and engages the rack, thus tending to frictionally hold the crosshead in any position to which it may have been moved by the operation of the spindle.

The spindle is preferably provided with a handwheel 13 of vulcanized tibre or other non-conducting material. The crosshead it self is also preferably formed of such material, while the extension 8 may be of metal.

A modified form is shown in Fig. 3. The plunger is rotatable by means of a hand wheel 1d secured to the lower end thereof and is threaded to engage a suit-able nut 15 secured in the crosshead. By the rotation of the plunger, the crosshead may be adjusted longitudinally of the spindle and the minimum speed of the motor thus varied.

What I claim is 1. In a rheostat the combination of a solenoid; a plunger forming the core of the solenoid; fixed contacts arranged in a series and connected with motor controlling resistances; a cross head connected with the plunger and adapted to engage the fixed contacts to vary the motor controlling resistances as th cross head is moved by the plunger; and means for adjusting the said cross head longitudinally of the plunger.

2. In a rheostat the combination of a solenoid; a plunger forming the core of the solenoid; fixed contacts arranged in a series and connected with motor controlling re Ristances; a cross head connected with the plunger and adapted to engage the fixed contacts to Yin the motor controlling; resistances as the cross head is moved, by he plunger; a rack formed on the plunger; 0

spindle join-nailed in the cross head; a pin- 1011 secured to said spindle and engaging the rack; and a click device engaging the rack to hold the cross head as moved by the operation of-the rack and pinion. 10

Signed at Toronto, Canada, this 28th day of Sept. 1923.

WILLIAM H. LESLIE. 

